The spread of personal computers and workstations has led to the development of networks for interconnecting such equipment and common resources such as printers and data storage devices. More powerful and sophisticated computing equipment and programs have progressively become available, allowing the processing of data in larger and larger quantities, for example in the form of database information and graphic images. These developments have in turn placed increasing demands on the speed and capacity of networks.
Various new networking technologies have been proposed to cater for these demands. One recent proposal has been established as IEEE Standard 802.12, and is also known as 100VG-AnyLAN. This technology, which transfers data at 100 megabits/s (Mb/s), involves splitting a data frame to be transmitted into consecutive blocks of five bits each, encoding the blocks using a 5B6B code, and distributing the encoded blocks among four twisted-pair conductors on a cyclic basis.
Although networks based on this technology are being deployed and meet current requirements, it is envisaged that future computing developments will eventually require even higher-speed and thus higher-capacity networks. However, to minimize the costs involved it is desirable to continue to use the same kind of cabling infrastructure as is being used for current networks. However, the use of such infrastructures requires conformance with strict regulatory limits on the level of radiated electromagnetic emissions having frequencies above 30 MHz. Simply increasing the bit rate of existing networking systems, for example, would result in unacceptable levels of such emissions.
It is an object of this invention to provide apparatus and methods for communicating data at data rates in excess of 100 Mb/s, using similar conductors to those now in use and conforming to regulatory requirements.